/** @param number the number to be tested
   *         Precondition: number > 0
   *  @return true if every decimal digit of number is a divisor of number;
   *          false otherwise
   */
  public static boolean isSelfDivisor(int number)
  {
    int n = number;
    while (n > 0)
    {
      int d = n % 10;
      if (d == 0 || number % d != 0)
        return false;
      n /= 10;
    }
    return true;
  } 1

1. Exam grading showed that almost half of the students decided to convert number into a string, then extract individual digits from the string and convert them back into ints.  Something like this:

     public static boolean isSelfDivisor(int number)
     {
       String s = String.valueOf(number);
       for (int i = 0; i < s.length(); i++)
       {
         int d = Integer.parseInt(s.substring(i, i+1));
         if (d == 0 || number % d != 0)
           return false;
       }
       return true;
     }

   Correct solutions of this kind did receive full credit.  However, the grading rubric was setup in such a way that flawed solutions using strings were graded more harshly.  In the real world, it would be in bad taste to unnecessarily convert a simpler data item (int) into a more complicated one (String).  In the context of the AP exam, it may be an expedient way to answer the question, if you know exactly what you are doing.

  /** @param start starting point for values to be checked
   *         Precondition: start > 0
   *  @param num the size of the array to be returned
   *         Precondition: num > 0
   *  @return an array containing the first num integers >= start that are self-divisors
   */
  public static int[] firstNumSelfDivisors(int start, int num)
  {
    int[] a = new int[num]; 1
    int count = 0;
    int n = start;
    while (count < num)
    {
      if (isSelfDivisor(n))
      {
        a[count] = n;
        count++;
      }
      n++;
    }
    return a;
  }

1. Do not forget to create the resulting array.